Because Beagles and Spaniel breeds are bred for things like hunting and foraging, they will always do it and digging is part of that. You'll find there is most likely something in the soil, a scent that is attracting them, possibly even a particular plant - if you have put blood and bone down anywhere in that garden at any point, that will be a definite trigger and you will likely never be able to get rid of it. Some terriers also have the digging instinct from their being bred for ratting. My parents have silky terriers, and Dad used to put pepper in the holes and it worked a treat. The dogs would stay away because they just couldn't handle the sneezing! Oh and if you have any chewing problems - probably that would be the Beagle's thing - tabasco sauce works miracles.

Bex - I wish our puppy was bothered by standing in her own poo - she does it ALL the time and tracks it around EVERYWHERE its disgusting. Wet grass though, you would think that was a mine field!